Multiple pole electrostatic chuck with self healing mechanism for wafer clamping

ABSTRACT

An electrostatic chuck device for clamping a semiconductor wafer substrate during processing of the semiconductor wafer includes a power source, at least one negative pole, and a plurality of positive poles. Each positive pole selected from the plurality of positive poles is electrically separated from the negative pole. Also provided is a plurality of fuses, each fuse of the plurality of fuses is coupled to an associated positive pole included in the plurality of positive poles. Each fuse is further coupled to the power source. In some embodiments, each positive pole is electrically separated from the negative pole by an insulating epoxy. In other embodiments, the plurality of positive poles are connected to each other in parallel.

BACKGROUND OF THE INVENTION

1. Field of Invention

The present invention relates generally to methods and apparatus for usein semiconductor fabrication. More particularly, the present inventionrelates to methods and apparatus for using a multiple pole configurationin an electrostatic chuck arranged to support a semiconductor waferduring semiconductor fabrication.

2. Description of the Prior Art

In the manufacture of semiconductor devices, the reliability and therepeatability of fabrication processes is crucial. That is, consistencyin semiconductor fabrication is important to ensure that the finalsemiconductor product is robust and functions as intended. The overallfabrication of semiconductor devices generally includes processes suchas etching, polishing, and deposition. As will be appreciated by thoseskilled in the art, etching processes, polishing processes, anddeposition processes typically require that a semiconductor wafer issecurely held, e.g., clamped.

In general, mechanical devices may be used to clamp a wafer duringprocessing. FIG. 1 is a diagrammatic cross-sectional representation of aconventional mechanical device used to clamp a semiconductor waferduring processing. A mechanical device 10 includes a base plate 14 andtop plates 18. A semiconductor wafer 22 is held between base plate 14and top plates 18. Specifically, wafer 22 is held such that a topsurface 24 of wafer 22 contacts top plates 18, while a bottom surface 26of wafer 22 rests against base plate 14.

The use of mechanical device 10 may cause inconsistencies in the overallprocessing of wafer 22. By way of example, during an etching processused to etch top surface 24, the portions of top surface 24 whichcontact top plates 18 may not be properly etched, as top plates 18generally obscure at least a portion of top surface 24. In other words,the edges of top surface 24 which are in contact with top plates 18 maynot be uniformly etched, thereby affecting the overall fabrication ofsemiconductors contained within wafer 22.

In order to eliminate contact between the top surface of a wafer and aclamping mechanism such as a top plate, electrostatic clamps, or chucks,are often used to secure a wafer that is being processed. Anelectrostatic chuck is generally arranged to use the force of attractionbetween a positive charge and a negative charge to produce a force thatis sufficient to hold a wafer in place. In other words, an electrostaticchuck uses forces created between a positive charge and a negativecharge to essentially clamp a wafer.

FIG. 2 is a diagrammatic representation of a bipolar electrostatic chuckdevice in accordance with prior art. A bipolar electrostatic chuckdevice 50 includes a base plate 54 and a positive electrode 58. As willbe appreciated by those skilled in the art, base plate 54 typicallyholds a negative charge, while positive electrode 58 holds a positivecharge. Base plate 54 and positive electrode 58 are generally separatedby a first insulator 60. A second insulator 62 is arranged over baseplate 54 and positive electrode 58 in order to insulate a semiconductorwafer 64 from electric charges associated with base plate 54 andpositive electrode 58. Wafer 64 is held against second insulator 62 whenan attraction between positive electrode 58 and base plate 54 causes anelectrostatic attraction between wafer 64 and positive electrode 58.

A power source 66 is arranged to apply voltage to base plate 54 and topositive electrode 58. No voltage is applied directly to wafer 64.Instead, as previously mentioned, the attraction between positiveelectrode 58 and base plate 54 causes wafer 64 to be attracted topositive electrode 58. Hence, wafer 64 may be secured against secondinsulator 62.

First insulator 60 is typically composed of a material with a highdielectric constant, such as an insulating epoxy. Second insulator 62 isalso typically composed from a material with a high dielectric constant,e.g., silicon dioxide or titanium dioxide. As will be appreciated bythose skilled in the art, if either first insulator 60 or secondinsulator 62 and "breaks down," bipolar electrostatic chuck device 50will fail, and wafer 64 will no longer be securely held. By way ofexample, when first insulator 60 breaks down, or degrades, positiveelectrode 58 will typically short against base plate 54, thereby causinga failure of bipolar electrostatic chuck device 50. Degradation of firstinsulator 60 may occur for any number of different reasons, including,but not limited to, extended exposure to chemicals such as chlorine andsulfur tetraflouride. Chlorine and sulfur tetraflouride are oftenpresent in plasmas used during semiconductor fabrication processes.

The failure of an electrostatic chuck device may cause significantproblems. For example, when an electrostatic chuck device fails, thedevice must generally either be repaired or replaced, thereby causingdowntime in the overall semiconductor fabrication process. Further, anysemiconductor wafer which is mounted on an electrostatic chuck device atthe time of failure may be damaged. Downtime in the overallsemiconductor fabrication process is undesirable in that it affects theefficiency of the fabrication process, whereas damage to a semiconductorwafer may cause reliability issues in semiconductor devices formed fromthe wafer. Therefore, what is needed is an improved electrostatic chuckdevice that is less likely to fail catastrophically.

DISCLOSURE OF THE INVENTION

An electrostatic chuck device for clamping a semiconductor wafersubstrate during processing of the semiconductor wafer substrate inaccordance with an aspect of the present invention includes: (a) a powersource; (b) at least one negative pole; (c) a plurality of positivepoles, wherein each positive pole selected from the plurality ofpositive poles is electrically separated from the negative pole; and (d)a plurality of fuses, each fuse of the plurality of fuses being coupledto an associated positive pole included in the plurality of positivepoles, wherein each fuse is further coupled to the power source. In someembodiments, each positive pole is electrically separated from thenegative pole by an insulating epoxy. In other embodiments, theplurality of positive poles are connected to each other in parallel.

In accordance with another aspect of the present invention, a method forforming an electrostatic chuck device for use in securing asemiconductor wafer substrate includes providing a power source andproviding a base plate which holds a negative charge and is arranged tosupport the semiconductor wafer substrate. The base plate is coupled tothe power source, and a first positive pole that is arranged to hold apositive charge is provided, along with a first fuse. The first fuse iscoupled to the first positive pole such that the first fuse is arrangedto deactivate the first positive pole when the first positive pole is nolonger isolated from the base plate. The first fuse is also coupled tothe power source, wherein the first positive pole and the base plate arearranged to create a first attraction force that is arranged to securethe semiconductor wafer substrate. In one embodiment, the methodincludes providing a second positive pole, coupling the second positivepole to the power source, providing a second fuse, and coupling thesecond fuse to the second positive pole.

The present invention provides an improved electrostatic chuck apparatusfor clamping a semiconductor wafer substrate during wafer fabricationthat includes multiple poles arranged in a grid configuration. Byproviding multiple poles and, further, by coupling the multiple poles tofuses, when an insulating layer which insulates positive charges fromnegative charges degrades, the redundancy afforded by the multiple polesgenerally renders the electrostatic chuck less as likely to suffer acatastrophic failure. If the insulating layer near one pole degrades,the fuse associated with that pole blows, and effectively "removes" thatpole from the grid configuration, thereby allowing the remainder of thepoles to continue functioning. Hence, rather than causing the entireelectrostatic chuck to fail catastrophically, a degradation in theinsulating layer generally does not significantly affect the overallelectrostatic chuck.

These and other advantages of the present invention will become apparentupon reading the following detailed descriptions and studying thevarious figures of the drawings

BRIEF DESCRIPTION OF THE DRAWINGS

The invention, together with further advantages thereof, may best beunderstood by reference to the following description taken inconjunction with the accompanying drawings in which:

FIG. 1 is a diagrammatic cross-sectional representation of aconventional mechanical semiconductor wafer clamping device.

FIG. 2 is a diagrammatic cross-sectional representation of aconventional bipolar electrostatic chuck device.

FIG. 3 is a diagrammatic cross-sectional representation of a multiplepole electrostatic chuck device in accordance with a first embodiment ofthe present invention.

FIG. 4 is a diagrammatic cross-sectional representation of the multiplepole electrostatic chuck device of FIG. 3 after a fuse has been blown inaccordance with the first embodiment of the present invention.

FIG. 5 is a diagrammatic cross-sectional representation of a multiplepole electrostatic chuck device in accordance with a second embodimentof the present invention.

BEST MODES FOR CARRYING OUT THE INVENTION

As noted previously, electrostatic clamps, or chucks, are often used tosecure a wafer that is being processed. The use of electrostatic chucks,which use the force of attraction between a positive electrode and anegative electrode to produce a force that is sufficient to hold a waferin place, eliminates physical contact between the top surface of thewafer and a clamping mechanism. If an insulator between the positiveelectrode and the negative electrode of an electrostatic chuck degrades,the positive electrode will generally short against the negativeelectrode, thereby causing a failure of the electrostatic chuck. Byimplementing multiple electrodes within an electrostatic chuck in aconfiguration that enables a wafer to remain clamped even with somedegradation in an insulator, the potential for a catastrophic failure ofthe electrostatic chuck may be reduced.

With reference to FIG. 3, a multiple pole electrostatic chuck devicewill be described in accordance with a first embodiment of the presentinvention. A multiple pole electrostatic chuck device 302 is arranged tosupport a semiconductor wafer substrate 303 includes a base plate 304,which holds a negative charge, and a plurality of positive poles 306a-g.The number of positive poles 306a-g included in electrostatic chuckdevice 302 may generally be widely varied, and is dependent upon factorssuch as the size of wafer substrate 303. By way of example, for a wafersubstrate with a diameter of approximately six inches, the use ofapproximately fifty positive poles may be preferred. Alternatively, fora wafer substrate with a diameter of approximately twelve inches, theuse of approximately one hundred positive poles may be preferred.

Positive poles 306a-g are each separated from base plate 304 by poleinsulators 312a-g, respectively. Pole insulators 312a-g are arranged toprevent positive poles 306a-g from shorting out against base plate 304.While pole insulators 312a-g may generally be formed from any suitablematerial, in one embodiment, pole insulators 312a-g are often made froman epoxy material with dielectric properties. Alternatively, in otherembodiments, pole insulators 312a-g may be formed from an anodizedmaterial or a ceramic film.

In general, pole insulators 312a-g may have substantially any suitablethickness. In other words, the separation between each positive pole306a-g and base plate 304 may be widely varied. For instance, a poleinsulator such as pole insulator 312a may have a thickness in the rangeof approximately one mil (i.e., 0.001 inches) to approximately fivemils, as for example approximately three mils.

An overlying insulator 316 is arranged over base plate 304 and positivepoles 306a-g to insulate wafer substrate 303 from electric chargesassociated with both base plate 304 and positive poles 306a-g. Like poleinsulators 312a-g, overlying insulator 316 may be formed fromsubstantially any suitable material with dielectric propertiesincluding, for example, epoxy, anodized materials, and ceramic.Overlying insulator 316, however, is generally thicker than poleinsulators 312a-g. Specifically, overlying insulator 316 typically has athickness in the range of approximately 2 mils to approximately 6 mils,although it should be appreciated that the thickness of overlyinginsulator 316 may vary.

A power source 308 is arranged to supply voltage to both base plate 304and positive poles 306a-g. As shown, power source 308 is coupled topositive poles 306a-g through fuses 310a-g, respectively. In thedescribed embodiment, positive poles 306a-g, are arranged in a grid,e.g., an electrostatic grid. That is, positive poles 306a-g are arrangedin parallel. Fuses 310a-g are arranged to ensure that the shorting ofany positive poles 306a-g associated with a given fuse 310a-g,respectively, against base plate 304, due to degradation of theassociated pole insulator 312a-g, does not result in a catastrophicfailure of electrostatic chuck device 302. By way of example, ifpositive pole 306a shorts out against base plate 304 due to degradationof pole insulator 312a, fuse 310a will "blow," and allow remainingpositive poles 306b-g to function, as will be described below withrespect to FIG. 4. When positive pole 306a fails, positive poles 306b-gmay continue functioning, since positive poles 306b-g are arranged inparallel with positive pole 306a. In other words, fuses 310a-gessentially serve as a self-healing mechanism which allows one positivepole 306a-g to be disabled, without disabling electrostatic chuck device302 as a whole.

In general, a fuse is rated for a maximum, or threshold, current level,and is arranged to blow when a metallic link within the fuse melts. Themetallic link in the fuse melts when a current that exceeds the maximumcurrent rating passes through the fuse. Fuses 310a-g may be ofsubstantially any type. Suitable fuses include, but are not limited to,any semiconductor or ferrule fuse, or other types of fuses rated forabout 1/10 Amps at 600 V or more.

FIG. 4 is a representation of multiple pole electrostatic chuck device302 of FIG. 3 after a fuse has been blown in accordance with the firstembodiment of the present invention. As shown, fuse 310a' is blown. Inthe described embodiment, fuse 310a' is blown when positive pole 306ashorts against base plate 304, which holds a negative charge. A short352, or short circuit, is often the result of a degradation of poleinsulator 312a. Short 352, as will be appreciated by those skilled inthe art, causes excessive current to flow from power source 308 topositive pole 312a. Fuse 310a' is blown when short 352 causes currentthat exceeds the maximum current rating of fuse 310a' to flow throughfuse 310a'.

When fuse 310a' is blown, positive pole 312a becomes essentially uselessin terms of creating an electrostatic attraction to secure wafersubstrate 303. However, redundancy is created in electrostatic chuckdevice 302 by positive poles 312b-g, as even without positive pole 312a,positive poles 312b-g still serve to secure wafer substrate 303.Therefore, the redundancy created by the use of multiple positive poles312a-g functioning in parallel prevents short 402 from causing acatastrophic failure of electrostatic chuck device 302.

In general, in a grid arrangement of positive poles 312a-g as shown,multiple positive poles 312a-g may be "inactivated," or otherwiserendered unusable due to shorts, before electrostatic chuck device 302is considered to fail overall. That is, wafer substrate 303 maygenerally be secured by electrostatic chuck device 302 until a"threshold" number of positive poles 312a-g fails. The minimum number ofpositive poles 312a-g needed to secure wafer substrate 303 againstelectrostatic chuck device 302 may be widely varied, and is dependent ona variety of different factors. The factors may include, but are notlimited to, the spacing between adjacent positive poles 312a-g, therelative strength of the attraction force associated with each positivepole 312a-g, and the size of wafer substrate 303. In one embodiment, fora wafer substrate with approximately a six inch diameter, ifapproximately fifty positive poles are included in an electrostaticchuck device that holds the wafer substrate, the failure of more thanapproximately twenty-five positive poles may cause the electrostaticchuck device to be unable to secure the wafer substrate. In other words,the wafer substrate may be secured using only approximately twenty-fiveof fifty total positive poles.

The number of positive poles 312a-g needed to secure wafer substrate 303may also be dependent upon the location of "functioning" positive poles.By way of example, in one embodiment, four positive poles may fail. Iffour positive poles were to fail, the force which with wafer substrate303 is held against electrostatic chuck device 302 is likely stronger ifpositive poles 312a, 312c, 312e, and 312g were to fail, rather than ifpositive poles 312a-d were to fail. In other words, the distribution ofthe attraction force may affect the number of positive poles 312a-gconsidered to be necessary to securely hold wafer substrate 303 againstelectrostatic chuck device 302.

FIG. 5 is a representation of a multiple pole electrostatic chuck devicein accordance with a second embodiment of the present invention. Anelectrostatic chuck device 402 which is arranged to support asemiconductor wafer substrate 403 includes a plurality of positive poles406a-g. Electrostatic chuck device 502 also includes a plurality ofnegative poles 404a-g, each of which is associated with a respectivepositive pole 406a-g. In one embodiment, negative poles 404a-gessentially form a base plate for electrostatic chuck device 402.

Positive poles 406a-g are separated from negative poles 404a-g,respectively, by pole insulators 412a-g. For example, positive pole 406ais separated from negative pole 404a by pole insulator 412a. Poleinsulators 412a-g are generally arranged to prevent positive poles406a-g from shorting out against negative poles 404a-g. While poleinsulators 412a-g may be formed from any suitable material, poleinsulators 412a-g are often made from an epoxy material which hasdielectric properties. Alternatively, pole insulators 412a-g may beformed from an anodized material or a ceramic film.

An overlying insulator 416 is arranged over negative poles 404a-g andpositive poles 406a-g to insulate wafer substrate 403 from electriccharges. Like pole insulators 412a-g, overlying insulator 416 may beformed from substantially any suitable material with dielectricproperties including, for example, epoxy, anodized materials, andceramic. As shown, overlying insulator 416 also serves to separateadjacent negative poles 404a-6.

A power source 408 is arranged to supply voltage to both negative poles404a-g and positive poles 406a-g. Power source 408 is coupled topositive poles 406a-g through fuses 410a-g, respectively. Fuses 410a-gare arranged to ensure that the shorting of any positive poles 406a-gagainst associated negative poles 404a-g does not result in acatastrophic failure of electrostatic chuck device 402, as describedabove with respect to FIG. 3.

Although only a few embodiments of the present invention have beendescribed, it should be understood that the present invention may beembodied in many other specific forms without departing from the spiritor the scope of the present invention. By way of example, the spacingbetween adjacent positive poles in a grid arrangement within anelectrostatic chuck may vary. That is, while the spacing betweenadjacent positive poles may be substantially uniform throughout theelectrostatic chuck, the spacing may also be vary between differentadjacent positive poles. The different spacing may be desirable if alarger concentration of positive poles is needed in a specific area,while fewer positive poles are needed in other areas.

As previously described, each positive pole in an electrostatic chuck iscoupled to a fuse. However, it should be appreciated that in someembodiments, such as embodiments which include a relatively large amountof positive poles, a plurality of positive poles may be coupled to asingle fuse. In other words, at least some fuses may be shared by morethan one positive pole. By allowing a plurality of positive poles toshare a single fuse, the number of fuses needed in an electrostaticchuck may be reduced, without greatly compromising the reliability ofthe electrostatic chuck. For example, if an electrostatic chuck includesapproximately fifty positive poles, twenty-five fuses may be used suchthat every two positive poles is coupled to a single fuse withoutdeparting from the spirit or the scope of the present invention.

Alternatively, it should be appreciated that in some embodiments, anelectrostatic chuck may include both positive poles which are coupled tofuses as well as positive poles which are not coupled to fuses. That is,only some of the positive poles included in an electrostatic chuck maybe coupled to fuses. By way of example, if certain poles within anelectrostatic chuck are observed to be less likely to fail, due todegradation in their associated pole insulators, fuses may notnecessarily be coupled to those poles.

While the use of fuses has been described above as being suitable forimplementation in an electrostatic chuck in accordance with the presentinvention, substantially any device which is arranged to stop the flowof current to a positive pole that is shorted out may be used in lieu offuses. Such alternate devices may include, but are not limited to, acrowbar circuit which has a self clamping design.

The thickness of pole insulators and an overlying insulator in anelectrostatic chuck device may generally be widely varied. Further, thethickness of each pole insulator included in an electrostatic chuck mayvary across the electrostatic chuck, i.e., the thickness of the poleinsulator around one positive pole may differ from the thickness of thepole insulator around another positive pole. In one embodiment, thethickness of a single pole insulator may also be non-uniform. Stillfurther, the polarity of the base plate and poles may be switched,depending on the arrangement of the power source, and therefore, it isnot a requirement that the base plate be negative and the poles bepositive.

Therefore, the present examples are to be considered as illustrative andnot restrictive, and the invention is not to be limited to the detailsgiven herein, but may be modified within the scope of the appendedclaims along with their full scope of equivalents.

What is claimed is:
 1. An electrostatic chuck device arranged to hold asemiconductor wafer substrate during processing of the semiconductorwafer substrate, the device comprising:a power source; a plurality ofnegative poles, each of the negative poles having a chuck surface and arecess formed through the chuck surface; a plurality of positive poles,wherein each positive pole selected from the plurality of positive polesis received in one of the recesses of a corresponding one of thenegative poles, each of the positive poles being electrically separatedfrom the corresponding negative pole; and a plurality of fuses, eachfuse of the plurality of fuses being coupled to an associated positivepole included in the plurality of positive poles, wherein each fuse isfurther coupled to the power source.
 2. An electrostatic chuck device asrecited in claim 1 wherein each of the positive poles selected from theplurality of positive poles and the corresponding negative pole areelectrically separated by an insulating epoxy, and each positive poleand corresponding negative pole form a separate chuck unit electricallyand physically separate from an adjacent separate chuck unit.
 3. Anelectrostatic chuck device as recited in claim 1 further including adielectric surface, the dielectric surface being arranged to contact thesemiconductor wafer substrate and to prevent the semiconductor wafersubstrate from directly contacting the plurality of negative poles andthe plurality of positive poles.
 4. An electrostatic chuck device asrecited in claim 3, the device further comprising:the plurality ofnegative poles being spaced to define separate chuck units; and thedielectric surface extending between the separate chuck units.
 5. Achuck device arranged to clamp a semiconductor wafer substrate duringprocessing of the semiconductor wafer substrate, the device comprising:abase plate, the base plate being divided into separate units, each ofthe units having a chuck surface and a recess extending from the chucksurface into the base plate, each of the base plate units being arrangedto hold a negative charge, wherein the base plate is arranged to supportthe semiconductor wafer substrate; a plurality of positive poles, eachof the positive poles being received in a respective one of the recessesand being arranged to hold a positive charge, wherein each of thepositive poles in a respective recess and the respective unit of thebase plate are arranged to create a separate attraction force; and aplurality of fuses, one of the plurality of fuses being coupled to arespective one of the positive poles, wherein each of the fuses isarranged to deactivate the respective positive pole when the respectivepositive pole comes into contact with the base plate.
 6. A chuck deviceas recited in claim 5 wherein each of the positive poles selected fromthe plurality of positive poles is separated from the respective unit ofthe base plate by an insulating material received in the respectiverecess.
 7. A method for forming an electrostatic chuck device for use insecuring a semiconductor wafer substrate, the methodcomprising:providing a power source; providing a base plate; dividingthe base plate into a plurality of electrically separate poles, each ofthe base plate poles being arranged to hold a negative charge and havingan open space defined therein, wherein the base plate is arranged tosupport the semiconductor wafer substrate; coupling each of the separatenegative poles of the base plate to the power source; providing aplurality of positive poles, each one of the positive poles beingpositioned in one of the open spaces of a respective negative pole;providing in each of the open spaces an insulating material to enableeach of the positive poles to hold a positive charge and each of thenegative poles to hold a negative charge; providing a plurality offuses; coupling one of the fuses to a respective one of the plurality ofpositive poles, wherein each of the coupled fuses is arranged todeactivate the respective positive pole when the respective positivepole comes into contact with the base plate; and coupling the pluralityof fuses to the power source, wherein coupled ones of the respectivepositive poles and negative poles of the base plate are arranged tocreate separate attraction forces, the attraction forces being arrangedto secure the semiconductor wafer substrate.
 8. A method as recited inclaim 7 further including:providing an insulator between each of thepositive poles and the respective separate pole of the base plate,wherein the insulator insulates each of the positive poles from each ofthe respective poles of the base plate.
 9. An electrostatic chuck devicearranged to hold a semiconductor wafer substrate during processing ofthe semiconductor wafer substrate, the device comprising:a power source;a plurality of positive poles; a plurality of negative poles spacedalong a workpiece axis, wherein each negative pole selected from theplurality of negative poles is provided with a cavity in which one ofthe positive poles selected from the plurality of positive poles isreceived; electrical insulation provided in each of the cavities toelectrically separate the negative poles from the positive poles andenable each of the corresponding respective positive poles in each ofthe respective cavities and each of the respective negative poles todefine a plurality of separate electrostatic chucks extending along theworkpiece axis; and a plurality of fuses, each fuse of the plurality offuses being coupled to an associated negative pole included in theplurality of negative poles, wherein each fuse is further coupled to thepower source.